Relevant bibliographies by topics / Functional megaspore

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Academic literature on the topic 'Functional megaspore'

Author: Grafiati
Published: 24 April 2022

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Journal articles on the topic "Functional megaspore"

1

Domaciuk, Marcin, Agata Leszczuk, Ewa Szczuka, Wioleta Kellmann-Sopyła, Justyna Koc, and Irena Giełwanowska. "Female sporogenesis in the native Antarctic grass Deschampsia antarctica Desv." Polish Polar Research 37, no. 2 (June 1, 2016): 289–302. http://dx.doi.org/10.1515/popore-2016-0016.

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Abstract The development of megasporocytes and the functional megaspore formation in Deschampsia antarctica were analyzed with the use of microscopic methods. A single archesporial cell was formed directly under the epidermis in the micropylar region of the ovule without producing a parietal cell. In successive stages of development, the meiocyte was transformed into a megaspore tetrad after meiosis. Most megaspores were arranged in a linear fashion, but some tetrads were T-shaped. Only one of the 60 analyzed ovules contained a cell in the direct proximity of the megasporocyte, which could be an aposporous initial. Most of the evaluated D. antarctica ovules featured monosporic embryo sacs of the Polygonum type. Approximately 30% of ovules contained numerous megaspores that were enlarged. The megaspores were located at chalazal and micropylar poles, and some ovules featured two megaspores – terminal and medial – in the chalazal region, or even three megaspores at the chalazal pole. In those cases, the micropylar megaspore was significantly smaller than the remaining megaspores, and it did not have the characteristic features of functional megaspores. Meiocytes and megaspores of D. antarctica contained polysaccharides that were detectable by PAS-reaction and aniline blue staining. Starch granules and cell walls of megasporocytes, megaspores and nucellar cells were PAS-positive. Fluorescent callose deposits were identified in the micropylar end of the megasporocytes. During meiosis and after its completion, thick callose deposits were also visible in the periclinal walls and in a small amount in the anticlinal walls of megaspores forming linear and T-shaped tetrads. Callose deposits fluorescence was not observed in the walls of the nucellar cells.
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2

Herd, Y. R., E. G. Cutter, and I. Watanabe. "An ultrastructural study of postmeiotic development in the megasporocarp of Azolla microphylla." Canadian Journal of Botany 64, no. 4 (April 1, 1986): 822–33. http://dx.doi.org/10.1139/b86-107.

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The development of megasporocarps of Azolla microphylla, after the retention of a single functional megaspore within the megasporangium, was studied by light and transmission electron microscopy, using material grown under controlled conditions. The young megaspore contained a thin layer of cytoplasm with various organelles and was bounded by a thin exine. It was surrounded by a dense periplasmodial tapetum, which consisted of a peripheral vacuolate region, containing degenerated megaspores, a middle region containing nuclei and large organelles such as amyloplasts and mitochondria, and an inner zone, invaginated round the spore, comprising microtubules, ribosomes, and coated vesicles. At a later stage the exine increased in thickness, and greater vacuolation occurred at the periphery of the periplasmodium. The endoperine was formed by deposition of granular material between the exine and the periplasmodium, and further granular material deposited in small vacuoles gave rise to the exoperine. The floats were formed from three (tapetal) membrane-bounded chambers, in which granular material gradually became organised to form the pseudocells. Characteristic exoperinal filaments were formed in channels in the periplasmodium, which was eventually completely used up in the formation of floats, collar, and megaspore wall, in which sporopollenin was probably present. The megaspore itself became engorged with cytoplasm and storage products such as lipid and starch. Cells of Anabaena with relatively thick walls were present between the megasporangial wall and the indusium.
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3

Norrmann, Guillermo A., and Camilo L. Quarín. "Permanent odd polyploidy in a grass (Andropogon ternatus)." Genome 29, no. 2 (April 1, 1987): 340–44. http://dx.doi.org/10.1139/g87-056.

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Andropogon ternatus is a triploid species (2n = 3x = 30) with a striking process of microsporogenesis that leads to the formation of two kinds of pollen grains. One-half of the grains carry only one 10-chromosome genome and the other half carry two genomes. After the first meiotic division in the megaspore mother cell, the micropylar daughter cell always has two nuclei, each with 10 chromosomes (genomes S and T); the chalazal daugher cell has one 10-chromosome set (genome S) and undergoes the second meiotic division giving rise to two megaspores; the one closer to the chalaza is the functional megaspore, while the other degenerates. The two-nucleate micropylar daughter cell remains undivided and then degenerates. Thus, the embryo sac always develops from a megaspore with 10 chromosomes (genome S). The results of interspecific crosses with a taxonomically related diploid species (A. selloanus) as well as the study of pollen grain development suggest that the grains carrying nuclei with 20 chromosomes (genomes ST) are functional in the fertilization process, while those with 10-chromosome nuclei seem to be ineffective. Therefore, A. ternatus is a sexual triploid that accomplishes the stability of its odd polyploid level by transmitting one genome through the egg cell and two genomes through the sperm nucleus. This is the first report of permanent odd polyploidy for a species of the monocotyledons. Key words: Gramineae, Andropogon ternatus, odd polyploidy, female meiosis, breeding systems.
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4

Yeung, Edward C., and Sandra K. Law. "Embryology of Epidendrum ibaguense. I. Ovule development." Canadian Journal of Botany 67, no. 8 (August 1, 1989): 2219–26. http://dx.doi.org/10.1139/b89-283.

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The orchids are unique among angiosperms in that ovule development is initiated after successful pollination. The monandrous orchid Epidendrum ibaguense has three placental ridges at anthesis. After pollination, mitotic activities result in the formation of a dichotomously branching system of outgrowths. The tip of each branch consists of five to six nucellar cells covered by the epidermis. A subterminal nucellar cell differentiates into the archesporial cell approximately 12 days after pollination. By day 18, it differentiates directly into a megasporocyte. The first meiotic cell division produces a dyad in which the micropylar cell begins prompt degeneration. The second meiotic cell division results in the formation of two megaspores of unequal size. The larger cell at the chalazal end will become the functional megaspore. Callose is present in the walls of the megasporocyte, the micropylar dyad cell, and the megaspore destined to degenerate. The development of the megagametophyte conforms to the Polygonum type. One of the chalazal nuclei delays its final mitotic division until fertilization, making it appear that only two antipodals are present. The mature ovules are bitegmic and have an anatropous orientation.
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5

Brukhin, Vladimir B., and Peter V. Bozhkov. "Female gametophyte development and embryogenesis in Taxus baccata L." Acta Societatis Botanicorum Poloniae 65, no. 1-2 (2014): 135–39. http://dx.doi.org/10.5586/asbp.1996.023.

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Crassinucellate ovules are initiated in <em>Taxus</em>, directly from the shoot apex. The rudimentary pollen chamber is formed in the nucellus. A linear tetrad of megaspores with a functional chalazal megaspore is formed. A free-nuclear stage is charac-teristic at the beginning of megagametophyte development. Archegonia without ventral canal cell are solitary or in complexes. The embryo has a very long suspensor even after maturation. Two types of polyembryony have been revealed: i) embryogenic redifferentiation of suspensor cells and ii) cleavage of embryonic region in the early embryo. In the northern temperate climate of St. Petersburg one month delay in development of reproductive structures has been noted.
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6

Núñez-Mariel, Citlali, E. Mark Engleman, and Judith Márquez-Guzmán. "Embriología de Pachycereus militaris (Audot) Hunt (Cactaceae)." Botanical Sciences, no. 68 (May 29, 2017): 5. http://dx.doi.org/10.17129/botsci.1632.

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This is a contribution to the embryology of cacti and to the definition of their reproductory structures. The development of anthers, ovules and seeds of Pachycereus militaris is described. The type of development of the anther wall is monocotyledonous. This may have taxonomic importance above the family level. The endothecium is formed by a single stratum and the pollen grains are tricolpate, spinulate and punctitegilate. A lineal triad of megaspores was observed. The functional megaspore is the chalazal one. It is proposed that the term campylotropous should be uti lized for describing the ovule type, while the term circinotropous should be reserved for the funicle. In contrast to the stated by other authors, this study suggests that the seeds of Pachycereus militaris should be considered as non-albuminous and non-perispermous.
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7

Gomez, Maria Dolores, Daniela Barro-Trastoy, Clara Fuster-Almunia, Pablo Tornero, Jose M. Alonso, and Miguel A. Perez-Amador. "Gibberellin-mediated RGA-LIKE1 degradation regulates embryo sac development in Arabidopsis." Journal of Experimental Botany 71, no. 22 (August 26, 2020): 7059–72. http://dx.doi.org/10.1093/jxb/eraa395.

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Abstract Ovule development is essential for plant survival, as it allows correct embryo and seed development upon fertilization. The female gametophyte is formed in the central area of the nucellus during ovule development, in a complex developmental programme that involves key regulatory genes and the plant hormones auxins and brassinosteroids. Here we provide novel evidence of the role of gibberellins (GAs) in the control of megagametogenesis and embryo sac development, via the GA-dependent degradation of RGA-LIKE1 (RGL1) in the ovule primordia. YPet-rgl1Δ17 plants, which express a dominant version of RGL1, showed reduced fertility, mainly due to altered embryo sac formation that varied from partial to total ablation. YPet-rgl1Δ17 ovules followed normal development of the megaspore mother cell, meiosis, and formation of the functional megaspore, but YPet-rgl1Δ17 plants had impaired mitotic divisions of the functional megaspore. This phenotype is RGL1-specific, as it is not observed in any other dominant mutants of the DELLA proteins. Expression analysis of YPet-rgl1Δ17 coupled to in situ localization of bioactive GAs in ovule primordia led us to propose a mechanism of GA-mediated RGL1 degradation that allows proper embryo sac development. Taken together, our data unravel a novel specific role of GAs in the control of female gametophyte development.
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8

Cheng, Chia-Yi, Dennis E. Mathews, G. Eric Schaller, and Joseph J. Kieber. "Cytokinin-dependent specification of the functional megaspore in the Arabidopsis female gametophyte." Plant Journal 73, no. 6 (January 18, 2013): 929–40. http://dx.doi.org/10.1111/tpj.12084.

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9

Folsom, M. W., and D. D. Cass. "Embryo sac development in soybean: ultrastructure of megasporogenesis and early megagametogenesis." Canadian Journal of Botany 67, no. 10 (October 1, 1989): 2841–49. http://dx.doi.org/10.1139/b89-365.

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The soybean ovule is bitegmic with the megasporocyte three to four cell layers beneath the nucellar epidermis. The megasporocyte is much larger than the surrounding nucellar cells, is connected to the nucellus by plasmodesmata, and at this stage exhibits a cytoplasmic density comparable with cells of the nucellus. After meiosis, the chalazal megaspore becomes functional in megagametogenesis. It alone retains plasmodesmatal connections to the nucellus. Chalazal megaspore expansion is accompanied by development of many small vacuoles having a uniform distribution. The first megaspore mitosis results in two nuclei lying on an axis parallel to the longitudinal axis of the embryo sac. Ultimately, these two nuclei are separated by a large vacuole. Numerous Golgi vesicles and proteinlike bodies are observed along the periphery of vacuoles in the 1-, 2-, and 4-nucleate embryo sacs. As the contents of vesicles and proteinlike bodies are observed deposited in vacuoles, it is probable that they both add osmotica to the vacuoles, thus promoting a water flux. We believe that the production of Golgi vesicles and putative protein bodies may be important in the formation and expansion of the large vacuole that appears to drive embryo sac expansion during early megagametogenesis in soybean. It is also believed that the timing to this vacuole's development has important developmental consequences.
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10

Cao, Ling, Sheng Wang, Prakash Venglat, Lihua Zhao, Yan Cheng, Shengjian Ye, Yuan Qin, Raju Datla, Yongming Zhou, and Hong Wang. "Arabidopsis ICK/KRP cyclin-dependent kinase inhibitors function to ensure the formation of one megaspore mother cell and one functional megaspore per ovule." PLOS Genetics 14, no. 3 (March 7, 2018): e1007230. http://dx.doi.org/10.1371/journal.pgen.1007230.

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